Re: How do I know if the timming is off?
Sir,
Symptoms of bad timing: Hard to start. Won't pull full RMP under load. Backfires. Knocking. Irregular idle. Runs hot. Burnt spark plugs. Stutter during acceleration. There are others but those are the main ones.
According to my manual, the '71 - '73s have flywheel magneto ignition systems and are safety protected by a vacuum "run away" safety switch.
The timing on these engines is set by the gaps on the points. This should be set at .020 (twenty thousandths).
Remove the flywheel, the ignition is underneath. (be careful, the groove for the starter rope and the starter teeth are easily damaged) Use a gear puller and the three tapped (1/4 - 20 thread) holes in the center. Set the flywheel aside, magnet side up, to prevent it from picking up metalic debris.
Remove the spark plugs to make the next step easier.
Bad points are pitted, warped, discolored, misaligned or bent. Replace them. Only a very minor imperfection is enough to throw timing way off.
Rotate the crankshaft until the keyway is pointed at the ignition points. That locates the high spot on the crankshaft cam lobe to fully open the points. Run a feeler gauge through the gap between the points. The gauge should just lightly drag on both sides of the points, not enough to move them further open. The center screw is the hold down, it needs to be loosened for you to be able turn the adjustment screw which has an elliptical head. Re-check the gap after tightening, often tightening the hold down screw will alter the gap you just set. Proceed to the next set of points.
While you're in there, closely examine the ignition coils for any sign of over-heating or damage. If there are any visable signs of damage, the coil should be replaced. If you're good with a multimeter you can check the coils electronically, the manual will give the proper resistance numbers for your ignition.
The spark plugs should be set to .030 gap (thirty thousandths) and torqued down to 210 - 246 inch pounds with NEW plug gaskets.
Not a difficult job, most people handy around boats can do it.
Do NOT hammer the flywheel back into place when rebuilding, use the crankshaft nut to pull it down. Be sure the key and keyway are free of dirt and debis.
